There’s no reason fore ugly black speakers. I have a set of speakers in rosewood cabinets that I made years ago. They sound great, but they are large. Years ago I got a deal on a case of Bose 4″, efficient, high power, full-range speakers. I built small enclosures for them and musicians bought them for monitors. I believe you could market paintings with speakers. You can get wireless speaker kits like this: https://smile.amazon.com/Rockler-Wireless-Speaker-Kit/dp/B0773N19CW/ref=sxbs_sxwds-stvp, and you could integrate it into the front or back of the paintings. You can also get fairly powerful, very small bluetooth amplifier boards to drive larger speakers. There are lots of ways to go with this.